linux-kernel - Re: [GIT PULL] arm64 updates for 6.13-rc1

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Message-ID: <dc5e8809-825f-4c38-b487-b16c7d516311@os.amperecomputing.com>
Date: Wed, 27 Nov 2024 17:21:37 -0800
From: Yang Shi <yang@...amperecomputing.com>
To: Catalin Marinas <catalin.marinas@....com>
Cc: Sasha Levin <sashal@...nel.org>,
 Linus Torvalds <torvalds@...ux-foundation.org>, Will Deacon
 <will@...nel.org>, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, David Hildenbrand <david@...hat.com>
Subject: Re: [GIT PULL] arm64 updates for 6.13-rc1

>> diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c
>> index 87b3f1a25535..ef303a2262c5 100644
>> --- a/arch/arm64/mm/copypage.c
>> +++ b/arch/arm64/mm/copypage.c
>> @@ -30,9 +30,9 @@ void copy_highpage(struct page *to, struct page *from)
>>    	if (!system_supports_mte())
>>    		return;
>> -	if (folio_test_hugetlb(src) &&
>> -	    folio_test_hugetlb_mte_tagged(src)) {
>> -		if (!folio_try_hugetlb_mte_tagging(dst))
>> +	if (folio_test_hugetlb(src)) {
>> +		if (!folio_test_hugetlb_mte_tagged(src) ||
>> +		    !folio_try_hugetlb_mte_tagging(dst))
>>    			return;
>>    		/*
> I wonder why we had a 'return' here originally rather than a
> WARN_ON_ONCE() as we do further down for the page case. Do you seen any
> issue with the hunk below? Destination should be a new folio and not
> tagged yet:

Yes, I did see problem. Because we copy tags for all sub pages then set 
folio mte tagged when copying the data for the first subpage. The 
warning will be triggered when we copy the second subpage.

>
> diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c
> index 87b3f1a25535..cc7dfbea1304 100644
> --- a/arch/arm64/mm/copypage.c
> +++ b/arch/arm64/mm/copypage.c
> @@ -30,11 +30,12 @@ void copy_highpage(struct page *to, struct page *from)
>   	if (!system_supports_mte())
>   		return;
>
> -	if (folio_test_hugetlb(src) &&
> -	    folio_test_hugetlb_mte_tagged(src)) {
> -		if (!folio_try_hugetlb_mte_tagging(dst))
> +	if (folio_test_hugetlb(src)) {
> +		if (!folio_test_hugetlb_mte_tagged(src))
>   			return;
>
> +		WARN_ON_ONCE(!folio_try_hugetlb_mte_tagging(dst));
> +
>   		/*
>   		 * Populate tags for all subpages.
>   		 *
>